The banks can come after you YEARS down the road for the money you owe. The rules are goverened by the state's, with some being worse then others. What most people don't realize is that the same holds true in a Short Sale. Usually the bank will have you sign a form that says you understand you are liable for the debt, and they can decide to come after you for it for x number of years.
In Florida the banks have up to 5 years to file for a deficiency judgement, and once granted they can attempt to collect for the next 20 years. Some states are tighter. Banks can tap your accounts or your pay check in order to recover the funds, with interest. I thought I heard of another state where the bank had x years past the original term of your loan to come after the debt. (Meaning if you had 25 years left on your mortgage they had 25+x years to get the money back)
Here's one article about it. It's been in our local news a lot recently because of the large number of forclosures and short sales in MI. You could search the http://www.freep.com page for the week long series they had, if you need to find more info for your hypothetical,
http://finance.yahoo.com/news/Mortgage-lenders-pursue-cnnm-3107909798.html?x=0
The number of deficiency judgements being filed by the banks are increasing, and people that 'strategically foreclosed' are going to be financially f^c#ed for quite some time.